Volume 12, Issue 2 (June 1990)

Compression tests on delaminated kevlar/epoxy specimens were conducted in order to determine the buckling and post-buckling behavior of the system and observe the characteristics of the deformation including growth of the delamination. A broad range of geometric configurations, as far as the location of the delamination through the thickness, was considered. Both the initiation resistance, defined as the applied displacement per specimen length and the growth resistance, defined as the applied displacement per unit delamination growth during the postbuckling stage were quantified for each configuration. For the particular case studied, it was found that the growth resistance is infinite (that is, no growth) for delamination thickness/total thickness ratio H/T = 1/15, becoming 0.52 for H/T = 2/15 and dropping to a value of only 0.07 for H/T = 4/15. The initiation resistance is also lowered as the delamination is located further away from the specimen surface and for H/T = 4/15 growth initiation occurred before peak load. The experimental program investigates also the development of the deformation regarding the postbuckled shape, the load-displacement curve and the corresponding growth of the delamination. Furthermore, a comparison with analytical solutions for the postbuckling behavior at large applied displacements is performed.